Field of the Invention
The present invention relates to a spacer and an expanding device for expanding the spacing between bones.
Description of the Related Art
Lumbar spinal canal stenosis is a disease in which the spinal canal is stenosed due to regressive degeneration of an intervertebral disc, ligament or the like, and which would cause such a symptom as lumbar pain, leg pain, or intermittent claudication. Treatment of the lumbar spinal canal stenosis is mainly carried out by an operation of resecting the vertebra in the part where the spinal canal is narrowed (laminectomy) or an operation of fixing the vertebra (spondylodesis). On the other hand, as a technique that is less invasive as compared with the laminectomy and spondylodesis, a method has been developed in recent years in which a metallic spacer is set indwelling in an interspinal area (between spinous processes) so as to remove a pressure on the spinal nerve or nerve root. This method, however, needs incision of muscles and ligament in the back in order to set the spacer indwelling in a desired area, so that the patient has to undergo such an invasive procedure and be kept hospitalized for a long period of time.
In order to solve these problems, another method has been proposed in which a spacer is inserted into an interspinal area in a less-invasive manner, to be left indwelling there. In this another method, first, a sheath is percutaneously inserted into the interspinal area. Then, an expandable spacer provided in a folded state at a distal end of a catheter is inserted and passed in the lumen of the sheath, to be disposed in the interspinal area. Thereafter, a filler such as bone cement is loaded into the spacer to expand the spacer, and the spacer is left indwelling in the interspinal area, or between spinous processes (see, for example, U.S. Patent Application Publication No. 2009/0118833). The filler is hardened after the spacer has been filled with the filler, so that the expanded state of the spacer can be maintained semi-permanently.